As processors have become more and more complex, the data carried by the bus has become further removed from the actual executed code inside the processor. Thus, a logic analyzer that is used to collect bus activity must differentiate between instructions that were actually executed and those instructions that were not. This task is difficult, at best. With the introduction of instruction and data caches in today's processors, tracking code execution at the bus seems illogical.
However, using a software trace technique facilitates the debugging of complex, target processors. Software trace provides the systems developer high-level source code that is correlated to a real-time trace acquired by a logic analyzer. Typically, the logic analyzer will use a disassembler to interpret which bus cycles contain code information. A symbol database is used to correlate the actual source code to the code addresses seen on the target bus. One limitation of this technique is that data operations that occur internally to the processor are not captured by the logic analyzer. Providing the developer with the relevant data operations would enhance the developer's knowledge of the processor during the debug stage of development.
Logic analyzers and related techniques for software debugging are disclosed in U.S. Pat. No. 4,373,193 for LOGIC STATE ANALYZER of George A. Haag, O. Douglas Fogg, Gordon A. Greenley, Steve A. Shepard and F. Duncan Terry; U.S. Pat. No. 4,720,778 for SOFTWARE DEBUGGING ANALYZER of Kevin M. Hall and Daniel A. Schmelzer; U.S. Pat. No. 5,450,586 for SYSTEM FOR ANALYZING AND DEBUGGING EMBEDDED SOFTWARE THROUGH DYNAMIC AND INTERACTIVE USE OF CODE MARKERS of Eric J. Kuzara, Andrew J. Blasciak and Greg S. Parets; and U.S. Pat. No. 5,737,520 for METHOD AND APPARATUS FOR CORRELATING LOGIC ANALYZER STATE CAPTURE DATA WITH ASSOCIATED APPLICATION DATA STRUCTURES of Robert D. Gronlund, Brian A. Willette and William M. Zevin. The foregoing patents are commonly assigned to Hewlett-Packard Company and are hereby incorporated herein by reference for all that they disclose and teach.